Dystonia as the Initial Manifestation of Moyamoya Disease: A Case Report and Literature Review.

Introduction: Moyamoya disease (MMD) is a progressive cerebrovascular disorder characterized by progressive narrowing of large intracranial arteries around the circle of Willis and the secondary development of collateral "moyamoya vessels." It typically presents with ischemic or hemorrhagic events, whereas movement disorders, particularly dystonia, are exceedingly rare initial manifestations. Case Reports: We report two adult cases of MMD initially presenting with hemidystonia. The first case involved a 27-year-old man with recurrent involuntary movements of the left limbs. Imaging revealed bilateral middle cerebral artery narrowing with collateral vessels and hypoperfusion of the right basal ganglia, without infarction or hemorrhage. The second case was a 25-year-old woman with a 2-year history of episodic left-sided dystonia, later complicated by contralateral spasms. Angiography demonstrated bilateral internal carotid artery occlusion with extensive collateralization, and perfusion magnetic resonance imaging showed reduced cerebral blood flow in the frontal and temporoparietal regions. She underwent encephaloduroarteriosynangiosis, resulting in resolution of dystonia but subsequent ischemic stroke. A literature review identified additional reports of dystonia as an uncommon manifestation of MMD, predominantly in pediatric populations. Conclusion: Our cases highlight that adult-onset MMD can present with dystonia in the absence of overt infarction, with chronic hypoperfusion of basal ganglia and cortical regions likely playing a key role. Medical therapy is generally ineffective, while revascularization may relieve symptoms, particularly when dystonia is perfusion-dependent; treatment strategies in adult MMD must be individualized, with careful consideration of bilateral disease severity and hemodynamic reserve. Recognition of dystonia as a rare presentation of MMD is important for timely diagnosis and individualized management.